Flushing shutters (tubs) are among the most efficient and most economical devices for cleaning settled sludge from settlement tanks. Flushing shutters are set in such a way that the tank can always be automatically flushed immediately after its emptying.
The shutter that is eccentrically suspended on bearings is filled with pumped water from an internal or external source. The shutter is overturned due to a change of its point of gravity just before its filling. The water stream then produces a strong wave whose flushing power is used to clean the tank and wash out the sediments to the drain pit.